Solid lipid nanocarriers embedded hydrogel for topical delivery of apremilast: In-vitro, ex-vivo, dermatopharmacokinetic and anti-psoriatic evaluation

The present work aimed to develop topical solid lipid nanocarriers (SLN) loaded hydrogel of apremilast (API) for psoriasis therapy to minimize the systemic adverse effects. The quality by design approach was implemented for the optimization of API loaded SLN using Box-Behnken design. SLN were prepared using hot emulsification followed by size reduction using probe sonication. The size and entrapment were found to be 167.70 nm +/- 1.5 (0.238 PDI) and 63.84 +/- 0.93%, respectively. The FESEM images of SLN dispersion portrayed the spherical shape of nanocarriers. The in vitro drug release of SLN dispersion showed extended-release up to 18 h and followed the Korsmeyyar-Peppas model with a regression value of 0.958 (n = 0.330), and Akaike index criteria was 63.69. In vitro cell line study, the MTT assay depicted the formulation excipients had minimal effect, and high internalization was observed with SLN dispersion (1.4-fold). The Ct value reduction in the relative expression of TNF-alpha miRNA was 3-fold higher with SLN dispersion compared to the positive control. The ex vivo skin retention and dermal distribution study by Coumarin-6 dye depicted an increase in permeation and retention with SLN formulation compared to free drug-loaded gel. The dermato-pharmacokinetic study of SLN formulation exhibited 2-fold higher drug retention in the epidermis and 5-fold higher in the dermis compared to free drug. This were stable for 3 months without significant changes. The results suggest that API loaded SLN can be utilized for topical delivery for effective treatment of psoriasis by targeting skin layers. The API loaded SLN based topical gel formulation showed improved permeation, skin deposition and prolonged release compared to conventional preparation. The designed preparation can signify a potential alternative for psoriasis treatment after clinical evaluation in near future.